/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_conv_partial_fast_opt_q15.c
 * Description:  Fast Q15 Partial convolution
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
  @ingroup groupFilters
 */

/**
  @addtogroup PartialConv
  @{
 */

/**
  @brief         Partial convolution of Q15 sequences (fast version).
  @param[in]     pSrcA      points to the first input sequence
  @param[in]     srcALen    length of the first input sequence
  @param[in]     pSrcB      points to the second input sequence
  @param[in]     srcBLen    length of the second input sequence
  @param[out]    pDst       points to the location where the output result is written
  @param[in]     firstIndex is the first output sample to start with
  @param[in]     numPoints  is the number of output points to be computed
  @param[in]     pScratch1  points to scratch buffer of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2
  @param[in]     pScratch2  points to scratch buffer of size min(srcALen, srcBLen)
  @return        execution status
                   - \ref ARM_MATH_SUCCESS        : Operation successful
                   - \ref ARM_MATH_ARGUMENT_ERROR : requested subset is not in the range [0 srcALen+srcBLen-2]

  @remark
                   Refer to \ref arm_conv_partial_q15() for a slower implementation of this function which uses a 64-bit accumulator to avoid wrap around distortion.
 */

arm_status arm_conv_partial_fast_opt_q15(
	const q15_t *pSrcA,
	uint32_t srcALen,
	const q15_t *pSrcB,
	uint32_t srcBLen,
	q15_t *pDst,
	uint32_t firstIndex,
	uint32_t numPoints,
	q15_t *pScratch1,
	q15_t *pScratch2)
{
	q15_t *pOut = pDst;                            /* Output pointer */
	q15_t *pScr1 = pScratch1;                      /* Temporary pointer for scratch1 */
	q15_t *pScr2 = pScratch2;                      /* Temporary pointer for scratch1 */
	q31_t acc0;                                    /* Accumulator */
	const q15_t *pIn1;                                   /* InputA pointer */
	const q15_t *pIn2;                                   /* InputB pointer */
	const q15_t *px;                                     /* Intermediate inputA pointer */
	q15_t *py;                                     /* Intermediate inputB pointer */
	uint32_t j, k, blkCnt;                         /* Loop counter */
	uint32_t tapCnt;                               /* Loop count */
	arm_status status;                             /* Status variable */
	q31_t x1;                                      /* Temporary variables to hold state and coefficient values */
	q31_t y1;                                      /* State variables */

#if defined (ARM_MATH_LOOPUNROLL)
	q31_t acc1, acc2, acc3;                        /* Accumulator */
	q31_t x2, x3;                                  /* Temporary variables to hold state and coefficient values */
	q31_t y2;                                      /* State variables */
#endif

	/* Check for range of output samples to be calculated */
	if ((firstIndex + numPoints) > ((srcALen + (srcBLen - 1U)))) {
		/* Set status as ARM_MATH_ARGUMENT_ERROR */
		status = ARM_MATH_ARGUMENT_ERROR;
	} else {
		/* The algorithm implementation is based on the lengths of the inputs. */
		/* srcB is always made to slide across srcA. */
		/* So srcBLen is always considered as shorter or equal to srcALen */
		if (srcALen >= srcBLen) {
			/* Initialization of inputA pointer */
			pIn1 = pSrcA;

			/* Initialization of inputB pointer */
			pIn2 = pSrcB;
		} else {
			/* Initialization of inputA pointer */
			pIn1 = pSrcB;

			/* Initialization of inputB pointer */
			pIn2 = pSrcA;

			/* srcBLen is always considered as shorter or equal to srcALen */
			j = srcBLen;
			srcBLen = srcALen;
			srcALen = j;
		}

		/* Temporary pointer for scratch2 */
		py = pScratch2;

		/* pointer to take end of scratch2 buffer */
		pScr2 = pScratch2 + srcBLen - 1;

		/* points to smaller length sequence */
		px = pIn2;

#if defined (ARM_MATH_LOOPUNROLL)

		/* Loop unrolling: Compute 4 outputs at a time */
		k = srcBLen >> 2U;

		/* Copy smaller length input sequence in reverse order into second scratch buffer */
		while (k > 0U) {
			/* copy second buffer in reversal manner */
			*pScr2-- = *px++;
			*pScr2-- = *px++;
			*pScr2-- = *px++;
			*pScr2-- = *px++;

			/* Decrement loop counter */
			k--;
		}

		/* Loop unrolling: Compute remaining outputs */
		k = srcBLen % 0x4U;

#else

		/* Initialize k with number of samples */
		k = srcBLen;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

		while (k > 0U) {
			/* copy second buffer in reversal manner for remaining samples */
			*pScr2-- = *px++;

			/* Decrement loop counter */
			k--;
		}

		/* Initialze temporary scratch pointer */
		pScr1 = pScratch1;

		/* Assuming scratch1 buffer is aligned by 32-bit */
		/* Fill (srcBLen - 1U) zeros in scratch buffer */
		arm_fill_q15(0, pScr1, (srcBLen - 1U));

		/* Update temporary scratch pointer */
		pScr1 += (srcBLen - 1U);

		/* Copy bigger length sequence(srcALen) samples in scratch1 buffer */

		/* Copy (srcALen) samples in scratch buffer */
		arm_copy_q15(pIn1, pScr1, srcALen);

		/* Update pointers */
		pScr1 += srcALen;

		/* Fill (srcBLen - 1U) zeros at end of scratch buffer */
		arm_fill_q15(0, pScr1, (srcBLen - 1U));

		/* Update pointer */
		pScr1 += (srcBLen - 1U);

		/* Initialization of pIn2 pointer */
		pIn2 = py;

		pScratch1 += firstIndex;

		pOut = pDst + firstIndex;

		/* Actual convolution process starts here */

#if defined (ARM_MATH_LOOPUNROLL)

		/* Loop unrolling: Compute 4 outputs at a time */
		blkCnt = (numPoints) >> 2;

		while (blkCnt > 0) {
			/* Initialze temporary scratch pointer as scratch1 */
			pScr1 = pScratch1;

			/* Clear Accumlators */
			acc0 = 0;
			acc1 = 0;
			acc2 = 0;
			acc3 = 0;

			/* Read two samples from scratch1 buffer */
			x1 = read_q15x2_ia(&pScr1);

			/* Read next two samples from scratch1 buffer */
			x2 = read_q15x2_ia(&pScr1);

			tapCnt = (srcBLen) >> 2U;

			while (tapCnt > 0U) {

				/* Read four samples from smaller buffer */
				y1 = read_q15x2_ia((q15_t **) &pIn2);
				y2 = read_q15x2_ia((q15_t **) &pIn2);

				/* multiply and accumlate */
				acc0 = __SMLAD(x1, y1, acc0);
				acc2 = __SMLAD(x2, y1, acc2);

				/* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
				x3 = __PKHBT(x2, x1, 0);
#else
				x3 = __PKHBT(x1, x2, 0);
#endif

				/* multiply and accumlate */
				acc1 = __SMLADX(x3, y1, acc1);

				/* Read next two samples from scratch1 buffer */
				x1 = read_q15x2_ia(&pScr1);

				/* multiply and accumlate */
				acc0 = __SMLAD(x2, y2, acc0);
				acc2 = __SMLAD(x1, y2, acc2);

				/* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
				x3 = __PKHBT(x1, x2, 0);
#else
				x3 = __PKHBT(x2, x1, 0);
#endif

				acc3 = __SMLADX(x3, y1, acc3);
				acc1 = __SMLADX(x3, y2, acc1);

				x2 = read_q15x2_ia(&pScr1);

#ifndef ARM_MATH_BIG_ENDIAN
				x3 = __PKHBT(x2, x1, 0);
#else
				x3 = __PKHBT(x1, x2, 0);
#endif

				/* multiply and accumlate */
				acc3 = __SMLADX(x3, y2, acc3);

				/* Decrement loop counter */
				tapCnt--;
			}

			/* Update scratch pointer for remaining samples of smaller length sequence */
			pScr1 -= 4U;

			/* apply same above for remaining samples of smaller length sequence */
			tapCnt = (srcBLen) & 3U;

			while (tapCnt > 0U) {
				/* accumlate the results */
				acc0 += (*pScr1++ * *pIn2);
				acc1 += (*pScr1++ * *pIn2);
				acc2 += (*pScr1++ * *pIn2);
				acc3 += (*pScr1++ * *pIn2++);

				pScr1 -= 3U;

				/* Decrement loop counter */
				tapCnt--;
			}

			blkCnt--;

			/* Store the results in the accumulators in the destination buffer. */
#ifndef  ARM_MATH_BIG_ENDIAN
			write_q15x2_ia(&pOut, __PKHBT(__SSAT((acc0 >> 15), 16), __SSAT((acc1 >> 15), 16), 16));
			write_q15x2_ia(&pOut, __PKHBT(__SSAT((acc2 >> 15), 16), __SSAT((acc3 >> 15), 16), 16));
#else
			write_q15x2_ia(&pOut, __PKHBT(__SSAT((acc1 >> 15), 16), __SSAT((acc0 >> 15), 16), 16));
			write_q15x2_ia(&pOut, __PKHBT(__SSAT((acc3 >> 15), 16), __SSAT((acc2 >> 15), 16), 16));
#endif /* #ifndef  ARM_MATH_BIG_ENDIAN */

			/* Initialization of inputB pointer */
			pIn2 = py;

			pScratch1 += 4U;
		}

		/* Loop unrolling: Compute remaining outputs */
		blkCnt = numPoints & 0x3;

#else

		/* Initialize blkCnt with number of samples */
		blkCnt = numPoints;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

		/* Calculate convolution for remaining samples of Bigger length sequence */
		while (blkCnt > 0) {
			/* Initialze temporary scratch pointer as scratch1 */
			pScr1 = pScratch1;

			/* Clear Accumlators */
			acc0 = 0;

			tapCnt = (srcBLen) >> 1U;

			while (tapCnt > 0U) {
				/* Read next two samples from scratch1 buffer */
				x1 = read_q15x2_ia(&pScr1);

				/* Read two samples from smaller buffer */
				y1 = read_q15x2_ia((q15_t **) &pIn2);

				/* multiply and accumlate */
				acc0 = __SMLAD(x1, y1, acc0);

				/* Decrement loop counter */
				tapCnt--;
			}

			tapCnt = (srcBLen) & 1U;

			/* apply same above for remaining samples of smaller length sequence */
			while (tapCnt > 0U) {
				/* accumlate the results */
				acc0 += (*pScr1++ * *pIn2++);

				/* Decrement loop counter */
				tapCnt--;
			}

			blkCnt--;

			/* The result is in 2.30 format.  Convert to 1.15 with saturation.
			 ** Then store the output in the destination buffer. */
			*pOut++ = (q15_t)(__SSAT((acc0 >> 15), 16));

			/* Initialization of inputB pointer */
			pIn2 = py;

			pScratch1 += 1U;

		}

		/* Set status as ARM_MATH_SUCCESS */
		status = ARM_MATH_SUCCESS;
	}

	/* Return to application */
	return (status);
}

/**
  @} end of PartialConv group
 */
